1. Field of the Invention
The present invention relates to a guide roller for handling traveling printed sheet, such as paper web, in a guide roller device of a rotary press, for example.
2. Description of the Related Art
Guide rollers in a guide roller device for a rotary printing press, for example, are arranged for guiding web traveling from a paper web supply section to a folding section through a printing section to desired orientations. Due to friction, the guide rollers are rotated at a peripheral substantially equal speed to the traveling speed of the traveling web.
Accordingly, foreign matters, such as ink and so forth may be transferred on the peripheral surface of the guide roller to contact with the web printed at the printing section. Such foreign matters adhering on the peripheral surface of the guide roller may cause scumming or tinting of the subsequently fed web to degrade printing quality. Furthermore, the foreign matters on the peripheral surface of the guide roller have to be removed by manual operation of personnel or by a special device during an interval of printing or after completion of printing.
As an approach for such drawback, the commonly assigned Japanese Unexamined Patent Publication 1-209139 proposes an improved guide roller device. The disclosed guide roller device includes two or more guide rollers. At least one of the guide rollers are associated through a torque transmission mechanism so as to rotate at a peripheral speed different from that of other guide rollers. The association of at least one of the guide rollers to others is so established as to rotate all of the guide rollers while establishing a balance of torque due to frictional forces acting between the outer peripheries of all guide rollers and the web for preventing the foreign matters, such as inks and so forth, from adhering by scrubbing of the web on the peripheral surface of the guide roller by providing slight difference of the peripheral speed of the guide roller and the traveling speed of the web. In addition, the disclosed guide roller device permits automatic sweeping of the guide roller.
The above-mentioned conventional device employs the frictional force between the web and the peripheral surface of the guide roller as driving force for rotation of guide roller, and adjusts the peripheral speed of the guide roller to be slightly different from the traveling speed of the web in self-adjusting manner within an allowable tension range of the web. This enables to scrub the web on the peripheral surface of the guide roller without causing unnecessary tension load on the web.
However, the above-mentioned conventional device requires the torque transmission mechanism for maintaining association of a plurality of guide rollers to make the construction complicated. In addition, associated works, such as maintenance and so forth is increased thereby increasing the cost.
On the other hand, the peripheral speeds of a plurality of guide rollers which are associated by the torque transmission mechanism associates and drives all guide rollers in the condition where torque by the frictional force acting between the peripheral surface of the associated guide rollers and the web is balanced. Accordingly, when the frictional force between one of the associated guide rollers and the traveling web is excessively larger than those of other guide rollers, such one of the guide rollers may rotate substantially irrespective of the rotation of other rollers so that the peripheral speed thereof and the traveling speed of the web becomes substantially equal to each other. Then, with to the peripheral surface of such guide roller, scrubbing effect by the traveling web is hardly expected.
On the other hand, in a large scale rotary press, such as a newspaper press, a feeding path of the medium from the feeding section to the folding section is substantially long. A plurality of guide rollers are arranged along the feeding path. The moment of inertia of rotation of these guide rollers is accumulated so that a substantially large inertia force is applied to the medium to cause various problems.
As a solution for this, Japanese Examined Patent Publication (Kokoku) No. 3-12541, Japanese Examined Utility Model Publication No. 3-6612, Japanese Unexamined Patent Publication (Kokai)No. 63-92564, Japanese Unexamined Patent Publication No. 3-286847 and Japanese Unexamined Patent Publication No. 4-89755 propose light weight rollers, which employ a fiber reinforced plastic cylinder as a primary material with fitting on the peripheral surface thereof a metal cylinder or a metal plating or the combination thereof, in order to reduce the moment of inertia.
Since the light weight roller is provided high rigidity and low moment of inertia, it may eliminate the drawback which otherwise encountered upon starting up and stopping. Also, for small moment of inertia, a tension to be applied to the medium becomes small to reduce contacting force between the medium and the light weight roller. This reduces adhering of the foreign matter. However, the latter problem, i.e. scumming or tinting of the peripheral surface of the guide roller, cannot be completely eliminated to require removal of the foreign matter with interrupting printing or after completion of printing.
Furthermore, the fiber reinforced plastic cylinder is formed by lamination of reinforcement fiber and the plastic, it has relatively low circularity and straightness. Therefore, the light weight roller employing such cylinder as the primary material tends to have relatively low rotating balance. Therefore, there is a need for the light weight roller to easily adjust the balance.